I’m sorry, but you really don’t have an understanding of what you are saying. For starters, are you referring to the Bolt, or the Carrier? All Carriers are actually made of 8620 Alloy steel. And they are either Phosphate, Nib, Nitride or other surface treatment/plating. C158 is an Low Alloy steel made by Carpenter, & NiB is a simply a plating Alloy substrate which is applied similar to any other plating process; in a Salt bath with electrical current. Just as ALL MilSpec Bolts are Phosphate coated, the steel underneath the NiB plating can still be C158, Or, as most BCG’s today are using 9310. Now 9310 is a Higher Alloy steel, and is a better choice steel in the end. As for all NiB Bolts breaking that you’ve seen, I find that maybe a bit unknowingly disingenuous. Unless you’ve seen a couple break? Then, sure. I can see that. I’ve seen many bolts break. MilSpec C158, 9310 Bolts & even the S7 “SUPER” Bolts by by Sharps. (Seen sever of those have the teeth shear off) However, I’m careful not to be misleading over one or another showing a 100% failure rate, which is kinda what you’re doing there.